1. Field of the Invention
The present invention relates to the field of radiofrequency engineering. It relates to a phase shifter arrangement and an antenna array having such a phase shifter arrangement.
2. Description of Related Art
In mobile radio technology, antenna arrays or antennas, in which two or more individual radiators are arranged one behind the other in a mounting direction and are driven via a common supply network, have long been known for equipping the base stations. In order to be able to take better account of the different conditions at the location of the respective base station and of the interaction with other base stations, it has proved to be advantageous to provide the antennas with the possibility of a “down tilt”. This may take place, in principle, by purely mechanical means by the antenna being designed such that it can be adjusted at the point at which it is fixed to the mast. One disadvantage of this is the fact that considerable complexity is required to adjust and alter such a mechanical down tilt and it is usually necessary to climb the mast for this purpose.
Several suggestions have therefore been made to carry out an “electrical down tilt” by, in the case of a fixed antenna, the individual radiators of the antenna or the antenna array being driven on different phases such that the radiation lobe formed by superimposing the phase-shifted arrays of individual radiators is tilted in a desired manner (“phased array”). Examples of such an electrical “down tilt” are disclosed in U.S. Pat. No. 6,198,458 or in U.S. Pat. No. 5,801,600 or in U.S. Pat. No. 5,905,462. Used here are special differential phase shifters (see also DE-A1-199 11 905 or U.S. Pat. No. 5,949,303) or other phase shifters which are arranged in the supply network of the antenna between the individual radiators and can be adjusted at the same time, for example, via a linkage by means of a motor drive (see also U.S. Pat. No. 5,798,675). The simple, electrically controllable adjustability in this case also provides the possibility of remote adjustment from a control center or the like (“remote tilt control”).
Combinations of mechanical and electrical down tilts are likewise conceivable (U.S. Pat. No. 5,440,318).
In more recent mobile radio transmission methods having a high data transmission rate, as are known, for example, by the abbreviation UMTS, the transition is increasingly being made to using “dual polarized antennas” in order to be able to make use of the effect of “polarization diversity” in which multiple transmission of data is possible on radio waves having a different polarization for the purpose of increasing transmission reliability. The radiators in these antennas in this case each have two radiator elements for the two polarizations and are in the form of, for example, cruciform dipoles or correspondingly designed patch radiators.
The document U.S. Pat. No. 6,310,585 discloses an electrically controlled down tilt by means of phase shifters for the dual polarized antennas or antenna arrays. For this purpose, each of the two radiator elements of a radiator within the supply network has in each case one associated phase shifter (40 in FIG. 1; 440 in FIG. 3), in which, for example, a microstrip line is overlapped to a greater or lesser extent by a displaceable dielectric (column 3, lines 61-65; column 5, lines 1-18). Details on the phase shifters and the associated microstrip lines are not given in the document.
In U.S. Pat. No. 6,310,585, the phase shifters for all of the radiator elements of one polarization direction are rigidly coupled mechanically to one another by means of a first rod. The phase shifters for all of the radiator elements of the other polarization direction are likewise rigidly coupled to one another mechanically by means of a second rod. The two rods, for their part, are rigidly connected to one another by means of a central supporting device (415 in FIG. 3) and are driven by a pinion via a toothed rack. In addition, two or more flexible positioning elements (420 in FIG. 3) are provided which press the dielectric against the microstrip lines below.
Disadvantages of this known phase shifter arrangement are not only the complex displacement mechanism comprising a plurality of individual elements, but also the separate structure of the individual phase shifters which requires high accuracy on assembly and thus increased mounting complexity with, at the same time, increased susceptibility to faults.